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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <functional>
#include <vector>
#include "mongo/base/init.h"
#include "mongo/db/exec/document_value/value.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/util/intrusive_counter.h"
namespace mongo {
/**
* Registers a GranularityRounder with the name 'name' and initializer key 'key'. When a
* granularity specification with name 'name' is found, 'rounder' will be called to construct a
* GranularityRounder for that granularity.
*
* Use this macro directly if you want 'name' and 'key' to be different. For example, this might be
* the case if 'name' is not a valid name for a C++ symbol (e.g. foo-bar). Otherwise, use
* REGISTER_GRANULARITY_ROUNDER instead.
*
* As an example, if you are adding a rounding granularity called foo-bar you would add this line:
* REGISTER_GRANULARITY_ROUNDER_GENERAL("foo-bar", foo_bar, GranularityRounderFooBar::create);
*/
#define REGISTER_GRANULARITY_ROUNDER_GENERAL(name, key, rounder) \
MONGO_INITIALIZER(addToGranularityRounderMap_##key)(InitializerContext*) { \
GranularityRounder::registerGranularityRounder(name, rounder); \
return Status::OK(); \
}
/**
* Registers a GranularityRounder to have the name 'key'. When a granularity specification with name
* 'key' is found, 'rounder' will be called to construct a GranularityRounder for that
* granularity.
*
* As an example, if you are adding a rounding granularity called foo you would add this line:
* REGISTER_GRANULARITY_ROUNDER(foo, GranularityRounderFoo::create);
*/
#define REGISTER_GRANULARITY_ROUNDER(key, rounder) \
REGISTER_GRANULARITY_ROUNDER_GENERAL(#key, key, rounder)
/**
* This class provides a way to round a value up or down according to a specific rounding
* granularity.
*/
class GranularityRounder : public RefCountable {
public:
using Rounder = std::function<boost::intrusive_ptr<GranularityRounder>(
const boost::intrusive_ptr<ExpressionContext>&)>;
/**
* Registers a GranularityRounder with a parsing function so that when a granularity
* with the given name is encountered, it will call 'rounder' to construct the appropriate
* GranularityRounder.
*
* DO NOT call this method directly. Instead, use the REGISTER_GRANULARITY_ROUNDER or
* REGISTER_GRANULARITY_ROUNDER_GENERAL macro defined in this file.
*/
static void registerGranularityRounder(StringData granularity, Rounder rounder);
/**
* Retrieves the GranularityRounder for the granularity given by 'granularity', and raises an
* error if there is no such granularity registered.
*/
static boost::intrusive_ptr<GranularityRounder> getGranularityRounder(
const boost::intrusive_ptr<ExpressionContext>& expCtx, StringData granularity);
/**
* Rounds up 'value' to the first value greater than 'value' in the granularity series. If
* 'value' is already in the granularity series, then it will be rounded up to the next value in
* the series.
*/
virtual Value roundUp(Value value) = 0;
/**
* Rounds down 'value' to the first value less than 'value' in the granularity series. If
* 'value' is already in the granularity series, then it will be rounded down to the previous
* value in the series.
*/
virtual Value roundDown(Value value) = 0;
/**
* Returns the name of the granularity series that the GranularityRounder is using for rounding.
*/
virtual std::string getName() = 0;
protected:
GranularityRounder(const boost::intrusive_ptr<ExpressionContext>& expCtx) : _expCtx(expCtx) {}
ExpressionContext* getExpCtx() {
return _expCtx.get();
}
private:
boost::intrusive_ptr<ExpressionContext> _expCtx;
};
/**
* This class provides a way to round a value up or down according to a preferred number series.
*
* The series that this class aims to support are specified here:
* https://en.wikipedia.org/wiki/Preferred_number
*/
class GranularityRounderPreferredNumbers final : public GranularityRounder {
public:
/**
* Returns a Granularity rounder that rounds according to the series represented by
* 'baseSeries'. This method requires that baseSeries has at least 2 numbers and is in sorted
* order.
*/
static boost::intrusive_ptr<GranularityRounder> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
const std::vector<double> baseSeries,
std::string name);
Value roundUp(Value value);
Value roundDown(Value value);
std::string getName();
/**
* Returns a vector that represents the preferred number series that this
* GranularityRounderPreferredNumbers is using for rounding.
*/
const std::vector<double> getSeries() const;
private:
GranularityRounderPreferredNumbers(const boost::intrusive_ptr<ExpressionContext>& expCtx,
std::vector<double> baseSeries,
std::string name);
// '_baseSeries' is the preferred number series that is used for rounding. A preferred numbers
// series is infinite, but we represent it with a finite vector of numbers. When rounding, we
// scale the numbers in '_baseSeries' by a power of 10 until the number we are rounding falls
// into the range spanned by the scaled '_baseSeries'.
const std::vector<double> _baseSeries;
std::string _name;
};
/**
* This class provides a way to round a value up or down to a power of two.
*/
class GranularityRounderPowersOfTwo final : public GranularityRounder {
public:
static boost::intrusive_ptr<GranularityRounder> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx);
Value roundUp(Value value);
Value roundDown(Value value);
std::string getName();
private:
GranularityRounderPowersOfTwo(const boost::intrusive_ptr<ExpressionContext>& expCtx)
: GranularityRounder(expCtx) {}
std::string _name = "POWERSOF2";
};
} // namespace mongo
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